The broad goals of this research project are to quantify real-world driving behavior in automobile drivers with obstructive sleep apnea (OSA) and to determine the amount of positive airway pressure (PAP) use needed to produce clinically meaningful improvements in driver safety. OSA causes cognitive impairments that increase the risk of driver errors that lead to a crash, which may be reversed with PAP treatment. However adherence to PAP therapy is a problem for many patients. Moreover, some individuals with OSA are not aware of their impairments, and are less likely to restrict themselves from driving despite being at increased risk for a crash. We propose that solutions to this problem can be derived through systematic behavioral and physiological measurements of patients in real world settings, using modern sensor technology. The specific aims of this translational research project are to 1) Quantify real-world driving performance in 75 drivers with OSA and 75 normal comparison drivers; 2) Determine the dose response relationship between PAP use and driver safety; and 3) Determine the factors that predict residual impairments in real-world driving performance in drivers with OSA after adjusting for levels of PAP use. To address these specific aims an interdisciplinary team of experts at UI will comprehensively assess 1) cognitive functions using standardized neuropsychological tests; 2) physiologic indices of disease severity from laboratory based polysomnography (PSG); 3) extended measurements of real-world PAP adherence, sleep patterns, and self-ratings of sleepiness and quality of life; and 4) extended observations of real-world driver performance and behavior from black box recorders in the drivers' own cars. The research team has expertise in sleep medicine, cognitive science, human factors engineering, biostatistics, and public policy. The project benefits from our long history of successful research using instrumented vehicles and a taxonomy for classifying and quantifying driver behavior. The statistical power of the study benefits from a longitudinal design, which correlates daily driving performance with PAP use each day for multiple consecutive days over 3 months. Our comprehensive approach to measuring disease-related clinical factors (i.e., pre-treatment AHI and oxygen saturation, BMI, self-reported sleepiness), cognitive impairment, and non-disease-related clinical factors (e.g., duration of nightly sleep) will enable us to determine the source of residual impairment in real-world driving performance in drivers with differing levels of PAP use. By tackling sleep and behavior research in real-world community settings, this study addresses an essential step in meeting the NIH priority of performing translational research by providing empirical data regarding PAP effectiveness and use. The patterns of performance and behavior observed in real-world OSA drivers can then be used to help formulate new hypotheses and treatment strategies for other sleep disorders, as well as for the broader issue of insufficient sleep in the general population.